A known approach for sensing current flow through a power transistor comprises a delta VBE (i.e. a voltage between a base and an emitter of a transistor) circuit using a metal resistor as a sensing element. One drawback of this approach is that the metal resistor consumes an undesirably large area. Another drawback of this approach is that the temperature-dependent resistance of the metal resistor causes a temperature-dependent error component in the sensed current flow.
European Patent Publication No. 0-481-328-A2 discloses a sensing circuit capable of being integrated into a self-isolated DMOST. The sensing circuit is driven by a sensor resistor that is created from the DMOST drain metallization. The sensing circuit produces an output current that is proportional to the DMOST current.
U.S. Pat. No. 5,767,545 to Takahashi discloses a current detection means for a power MOSFET (metal oxide semiconductor field effect transistor). A series circuit of a sensing MOSFET and a converting MOSFET is connected in parallel to the power MOSFET. The converting MOSFET converts a shunted current flowing through the sensing MOSFET into a voltage signal.